/*
 * Copyright 2020-2030 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.wwl.stackedQueue;

import java.util.Stack;

public class StackedQueue<T> {

    private Stack<T> stack;
    private Stack<T> stack2;
    private T front;

    public StackedQueue() {
        stack = new Stack<>();
        stack2 = new Stack<>();
    }

    public void push(T t) {
        if (stack.isEmpty()) {
            front = t;
        }
        stack.push(t);
    }

    public T pop() {
        if (!stack2.isEmpty()) {
            return stack2.pop();
        }
        while (stack.size() > 1) {
            stack2.push(stack.pop());
        }
        return stack.pop();
    }

    public T peek() {
        if (!stack2.isEmpty()) {
            return stack2.peek();
        }
        return front;
    }

    public boolean empty() {
        return stack.isEmpty() && stack2.isEmpty();
    }

}
